The present invention relates to an improved micro-computer operated control device for an air conditioning system which is capable of provision of varied air volume by a fan the operation speed of which can be controllably changed by way of adjustment of the voltage of the motor of the fan. The present invention is equipped with a number of temperature sensing components, a processing unit, a function setting unit, an output control unit and a power supply unit. When the air conditioning system of the present invention is started to operate, the processing unit begins to constantly make comparisons of the temperatures obtained from the temperature sensing components with those predefined temperatures in the function setting unit; and the results of the comparisons are transformed into corresponding control signals which are transmitted to the output control unit so as to make the voltage regulator thereof respond according to the control signals to vary the supplied voltage of the motor of a fan, resulting in the variation of the operation speed of the fan whereby the air volume delivered by the fan can be accordingly altered in response to the external environment constantly.
Generally, the prior art fan 15 in a conventional micro-computer controlled air conditioning system is controlled by a CPU which can constantly make comparisons of the external temperature related values with the predefined temperatures therein so as to be able to vary the operation speed of a 3-stage motor 151 of the fan 15 accordingly along with the heat or cool supplied by the air conditioning system simultaneously altered in accordance to the results of the comparisons. As shown in FIG. 2, the control of the supply of heat or cool is effected by way of a microcomputer controlled device in operation panel 25, supplied by D.C. power source 24, and fed to control circuit 22 through delivering circuit 23 having a control terminal 221 which is used to control, as shown in FIG. 1 a refrigerator 11 or a boiler 12 to start or stop functioning; and another control terminal 222 is used to control the opening and closing of a valve 14 so as to effect the variation of the supply of heat or cool to a closed space.
This kind of prior art can only vary the operation speed of the 3-stage motor 151 by way of the control terminals 223-225 and 226 through electrical operated three passage or two passage valve 26; the motor operating only at 3 different speeds can not vary the air volume supplied by the fan 15 linearly in correspondence to the external temperature changes from temperature sensors 20 through analog to digital converter 21 to delivering circuit 23. As shown in FIG. 3, in the three stages (indicated by a-b, b-c, c-d), the 3-stage motor 151 can operate only at a fixed speed Fs. Therefore, in each stage, the fan supplies a constant volume of air without any response to the external variation in temperature in a closed space 10, often making the closed space 10 too cold or hot for people to stay therein with comfort.